Do you have a sense of what proportion of biomass they made up from 1900-1950?

I happen to strongly agree that moral discount rate should be 0, but a) it's still worth acknowledging that as an assumption, and b) I think it's easy for both sides to equivocate it with risk-based discounting. It seems like you're de facto doing when you say 'Under that assumption, the work done is indeed very different in what it accomplishes' - this is only true if risk-based discounting is also very low. See e.g. Thorstad's Existential Risk Pessimism and the Time of Perils and Mistakes in the Moral Mathematics of Existential Risk for formalisms of why it might not be - I don't agree with his dismissal of a time of perils, but I do agree that the presumption that explicitly longtermist work is actually better for the long term than short-to-medium-term focused work is is based on little more than Pascalian handwaving.

I'm confused by your paragraph about insurance. To clarify:

• I don't expect insurance companies to protect against either extinction catastrophes or collapse-of-civilisation catastrophes, since as you say such catastrophes are uninsurable.
• I suspect they also don't protect against medium-damage-to-civilisation catastrophes for much the same reason - I don't think insurance has the capacity to handle more than very mild civilisational shocks.
• I do think government organisations, NGOs and academics have done very important work in the context of reducing risks of civilisation-harming events.
• I think that if you assign a high risk of a post-catastrophe civilisation struggling to flourish (as I do), these events look comparably as bad from a long-term perspective as extinction once you also account for their greater likelihood. I suggested a framework for this analysis here and built some tools to implement it described here.

Of course you can disagree about the high risk to flourishing from non-existential catastrophes but that's going to be a speculative argument about which people might reasonably differ. To my knowledge, no-one's made the positive case in depth, and the few people who've looked seriously into our post-catastrophe prospects seem to be substantially more pessimistic than those who haven't. See e.g.:

• Dartnell - 'we might have scuppered the chances of any society to follow in our wake'
• Rodriguez - 'humanity might be stagnant for millennia'
• Jebari - 'the development of industrialisation depends on more factors, and is more of a "lucky shot", than we might otherwise think'

Thanks - agree or disagree with it, this is a really nice example of what I was hoping for.

The extent to which you think they're the same is going to depend heavily on 

1. your long term moral discounting rate (if it's high, then you're going to be equally concerned between highly destructive events that very likely won't kill everyone and comparably destructive events that might),
2. your priors on specific events leading to human extinction (which, given the lack of data, will have a strong impact on your conclusion), and
3. your change in credence of civilisation flourishing post-catastrophe.

Given the high uncertainty behind each of those considerations (arguably excluding the first), I think it's too strong to say they're 'not the same at all'. I don't know what you mean by fields only looking into regional disasters - how are you differentiating those investigations from the fields that you mention that the general public has heard of in large part because a ton of academic and governmental effort has gone into it? 

I'm not sure I take a throwaway comment by someone closely socially tied to the author of the comment as evidence that it isn't equivalent. 

Also it doesn't need to be literally equivalent to them. The criticism, if there is one, would be that Scott's concept doesn't add anything to the work done by academics - although that criticism would be false if it unified hitherto un-unified fields in a useful way.

Do you have a citation for coordination traps specifically? Coordination games seem pretty closely related, but Googling for the former I find only casual/informal references to it being a game (possibly a coordination game specifically) with multiple equilibria, some worse than others, such that players might get trapped in a suboptimal equilibrium.

Noisy channel coding theorem 

I had the impression there was a field of '(global) resilience studies' I'd seen before, but on a first look at the moment can't find anything convincingly on point.